Changes to fisheries science urged
3 May 2012, by Tom Marshall
Scientists should change how they study the relationships between fish and their habitat, according to a recent report.
Research tends to be spread across areas of ocean that are too big to pick up complex local variations in fish habitat choices. It also puts excessive focus on physical properties such as temperature, salinity and depth at the expense of biological factors like the intricate relationships between predators and prey.
It's an important subject, because we still know surprisingly little about the lives of the fish around the UK and where in the ocean to focus conservation efforts. A lot of research is going on to try to change that, but this new study suggests we could be getting more bang for our buck.
'We invest millions in trying to find out where fish live, and why,' says Andrew Johnson, a PhD student in marine ecology at Bangor University and lead author of the paper. 'But we're neglecting some very important issues. We often look at fish habitat relationships over very large spatial scales, and we're also focusing heavily on abiotic habitat variables, mainly because they're much easier to measure and we have an abundance of these data.'
The paper analyses 109 studies describing the relationship between cold-water, bottom-dwelling fish species and their habitats, looking at the different spatial scales each examined, as well as the habitat variables they measured.
The researchers show that the bias towards larger areas and non-biological habitat variables isn't justified, and that these studies are not providing enough new information about the habitat needs of fish. Instead they suggest we need to invest more in studying biological habitat variables and smaller scales.
Johnson adds, 'Historically, research has also concentrated on species of commercial importance, neglecting those species of conservation concern such as skate and ray, few of which are now commercially viable.'
The main problem with the skewed focus of research, he explains, is that efforts to manage our fish stocks using areas closed to fishing are likely to be implemented over comparatively small scales. The UK is planning a coherent network of Marine Protected Areas (MPAs) by late 2012, and few of these areas match the common scales noted in the study. This means we need more detail from future studies if we're to work out exactly where to put such small MPAs to give the biggest possible boosts to marine biodiversity.
Even these small areas can be very beneficial if sited correctly. For instance, the No-Take Zone that prevents fishing around the island of Lundy in the Bristol Channel covers just a few square kilometres, but safeguards some of the richest reef habitats around Britain.
Yet conducting this research is no easy task. Many research vessels can sample the ocean's physical properties as a matter of course, but assessing levels of biological activity and ecosystem dynamics within an area is much harder.
Scientists will need to rely on time-consuming methods such as visual censuses and analyses of marine communities. For example, analysing fish stomach contents can provide information about food web dynamics and the often-overlooked habitat variables of predation, prey resource and competition.
Johnson says we also need more studies that carry on over long periods, to give us a better idea of how habitat use by fishes changes over time and how management strategies are working.
The NERC-funded study is published in Fish and Fisheries.
Linking temperate demersal fish species to habitat: scales, patterns and future directions. Andrew F Johnson, Stuart R Jenkins, Jan G Hiddink, Hilmar Hinz. Fish & Fisheries (2012). DOI: 10.1111/j.1467-2979.2012.00466.x
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